All of the songs on PianoTrax are played by a professional pianist.
Almost all of the tracks are recorded by Thomas Griep. He has conducted or played for many artists including: Carol Channing, Nathan Lane, Rita Moreno, Tommy Tune, Melissa Manchester, Loretta Devine, Olivia Newton-John, Kate Shindle, Lea Salonga, Lindsey Mendez, Leslie Odom, Jr. and Sutton Foster.
It requires a lot of experience for the accompanist to know if the sheet music should be played exactly as written or leave out the doubled melody in the accompaniment so the vocalist has some vocal freedom. Most of the tracks on the site have a "melody" version to help you learn the song and a "piano" version to perform with.